Well, I'm doing this on and off, may be around 2 months. The difficult part is the beginning because I don't usually use zbrush when it come to hard edge. So I have to learn a lot. But towards the end it became easy. Also another factor that slow me down is the my system. Since my machine is only running at 2GB, a lot of time I have to separate the ztools intead of one, just the retain the details.